Update VSM maturity score to minimal

Why is this change being made?

Value stream management's maturity score should be Minimal. https://gitlab.com/groups/gitlab-org/-/epics/7800#note_902448786

Looking at the definition for Viable I’ve marked what I believe to be true (👍), false (🙅) and not sure (🤔):

• 🙅 Significant use at GitLab the company.
• 🙅 CM Scorecard at least 3.14 for the job to be done (JTBD) when tested with internal users.
• 👍 No assessment of related jobs to be done.
• 🤔 Suitable to replace the need for existing tools for new namespaces, projects, and environments.

As a result I think it makes sense to change the maturity to Minimal.

Updating the maturity SSOT to the correct value so the knowledge isn't lost when @danmh transfers to Certify.

This change also updates the scorecard grade for VSM. The original scorecard scored 2 different experiences (gitlab-org&1454). With the score for the category now known as VSM being F.

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